Dato0011
Posts: 11
Joined: Tue Jul 22, 2014 8:25 am

How long can GPIO cables be?

Wed Oct 29, 2014 1:16 pm

Hi

I'm developing a project, where I need several hardware to be placed about ~1 meter apart from RPi. Those hardware will be wired using GPIO pins. So I'm interested if this will work. I heard that long cables can cause some problems. What is the recommended max length range? How can we overcome those limits?

Thanks.

Ravenous
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Location: UK

Re: How long can GPIO cables be?

Wed Oct 29, 2014 2:18 pm

I think for simple digital on/off signals I suppose a metre will be fine. (Unless perhaps extremely thin wire is used? Just a thought.)

If you're using something more complicated like I2C then it might cause problems. That was really intended for connecting chips in the same device.

As far as overcoming any limits, if the simple wire connection isn't good enough maybe some simple buffer chips could be used to drive the cables with a better current & voltage... or opto isolators or something like that. But I'd go for simple wires first.

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mikronauts
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Re: How long can GPIO cables be?

Wed Oct 29, 2014 3:35 pm

if there is significant electrical noise in the area, or varying strong magnetic fields, that signal becomes a 1M antenna...

At a minimum, I'd have a ground on each side of the signal, or better yet, a shielded cable, with the shield grounded.

Best of all: have an opto isolator at each end, and use say 5V or more for the signal.

Having said all that, if you are in a low electric noise environment, you may be OK - for example, in my lab at home, it would be be fine.
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ReBoot
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Re: How long can GPIO cables be?

Mon Nov 10, 2014 2:13 pm

I control (and feed) 2 servos at home via a 3m RS232 cable and it works just fine. AFAIK the cable is shielded.

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